Electric cars and biofuels seem to inhabit different universes these days. Nissan, General Motors, Toyota, Volkswagen, Honda, Ford, BMW, Tesla Motors, Fisker Automotive and Daimler, among others, have unfurled plans to release affordable electric cars over the next few years. Thousands of consumers have plunked down deposits on upcoming models and states have sought grants to pay for charging networks.

Meanwhile, biofuel startups, struggling for cash, have branched into jet fuel, chemicals and food additives as a way to get revenue to come in the door.

The liquid versus electrolyte debate, however, is not over, according to Britta Gross, the director of the energy systems group intelligence center at General Motors. Gross' job is to examine the costs/ benefits of the different propulsion systems for cars and the corresponding infrastructure. (Editor's Note: we spoke to her right before GM filed for its IPO.)

Liquids, in fact, may well play a larger role on weaning the world of gas in the foreseeable future, she said.

"Ethanol and biodiesel will be important as the lowest cost, near-term solution," she said. "The whole ethanol strategy is a get-off-gas strategy."

Why? Her thoughts below. You may not fully agree -- and as a GM employee, Gross is gung-ho on the plug-in Volt, too -- but it's an interesting point of view.

--Ethanol cars cost less. A car that runs on E85, or 85 percent ethanol, only costs a few hundred dollars more to make than an equivalent gas car. "The incremental cost is affordable," she said.

Producing a similar green diesel adds $3,000. A plug-in hybrid or all-electric costs even more to manufacture. Advantage: ethanol.

--Electric cars will likely always carry a premium. Batteries for electric cars now cost around $700 per kilowatt hour. While that price will decline, it won't be a precipitous decline.

"Some people are unrealistic" when it comes to estimating how cheap lithium batteries will become, she said. "Batteries are going to end up being more expensive than combustion engines."

--Ethanol is already in the market and so are the cars. "Ethanol has displaced 5 percent of the gasoline consumed in vehicles," Gross pointed out.

"We will be at the point soon where we have to put corn ethanol into E85 soon," she said. "We have to have a place to put corn ethanol . (...) We have got to build more E85 infrastructure."

--In terms of cost, ethanol (with subsidies) is comparable to gas in many regions where the pumps exist. (We didn't discuss alternatives to corn, but most cellulosic ethanol makers are still in the prototype production stage at best, so it will be a while.)

--Infrastructure in many ways could be easier and/or more cost-effective to build for ethanol than for electric cars. A filling station can serve hundreds of customers. By contrast, most consumers will charge electric cars at home, which means that most charging stations will serve only one family. GM deliberately designed the Volt so that it could be charged with an ordinary household outlet.

"There is a lot of money going into what seems to be a lot of infrastructure that could be under-utilized," she said.

--Range anxiety isn't dead yet. Most electric cars will be small- to mid-sized cars, partly as a result of this.

--Hydrogen isn't dead yet, either. It won't happen tomorrow, but GM (like Honda and Toyota) still sees promise in the concept. A hydrogen car is effectively an electric car that can be refueled in minutes and go further before refueling. Hydrogen is also arguably clean. Even if the hydrogen comes from cracking methane, a hydrogen car will emit 60 percent less greenhouse gases than a conventional gas car, she said. And like ethanol, a charging station can serve hundreds of consumers.